Fossils Provide Clues to Evolution of Flowers.

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Daffodils, tulips, roses, and other flowers are so much a part of our daily lives that we take them for granted. To evolutionary scientists, though, the question of how and when flowering plants appeared on Earth has gone unanswered for more than a century.

Mosses were the first plants to emerge on land around 425,000,000 years ago, followed by firs, ginkgoes, conifers, and several other varieties. According to the fossil record, flowering plants abruptly appeared out of nowhere about 130,000,000 years ago. Where did they come from, and how could they have evolved so suddenly without any transitional fossils linking them to other ancient plant species?

"An abominable mystery" is how 19th-century naturalist Charles Darwin referred to the origin of flowering plants, and the puzzle remains as controversial today as ever. Now, a team of Stanford (Calif.) University geochemists has entered the debate with evidence that flowers may have evolved 250,000,000 years ago--long before the first pollen grain appeared in the fossil record.

"Our research indicates that the descendants of flowering plants may have originated during the Permian period, between 290 and 245,000,000 years ago," says J. Michael Moldowan, research professor of geological and environmental sciences. "We based our findings on an organic compound called oleanane, which we found in the fossil record." Oleanane is produced by many common flowering plants as a defense against insects, fungi, and various microbial invaders, but is absent in other seed plants, such as pines and gingkoes.

Using gas chromatography and mass...